Polar modulation is a technique whereby a signal, or carrier, having constant radian frequency ω, is time-varied in both magnitude and phase. Polar modulation transmitters transmit information that both the magnitude (R) and the phase (θ) of a signal simultaneously carry. There are many benefits to using polar modulation to transmit information. Polar transmitters receive baseband signals represented in Cartesian form as an in-phase (I) component and a quadrature (Q) component. The I/Q baseband signals are naturally symmetric at the source. The I/Q baseband signals are converted to polar form in terms of its magnitude R and phase θ signals. The magnitude R is referred to as the amplitude signal and the phase θ is referred to as the phase signal. A coordinate rotation digital computer (CORDIC) algorithm may be employed to convert the I/Q baseband signals to polar form amplitude R and phase θ signals. The amplitude R and phase θ signals are processed in separate amplitude and phase paths and may be recombined at the output of the power amplifier. The I/Q components may be reconstructed by additional processing downstream of the power amplifier output.
Circuits for processing the amplitude R and phase θ signals in the respective separate amplitude and phase paths are substantially different and may lead to timing misalignments between the amplitude and phase signals. Unlike the natural symmetry of the I/Q baseband signals at the source, the amplitude R and phase θ signals are asymmetric, and thus, there are timing misalignments between them. The timing misalignment between these signals is detrimental to the reconstructed I/Q component. Accordingly, in polar transmitters, there is a need to synchronize the amplitude R and phase θ signals to correct for the timing misalignments due to different delays encountered by these signals in the separate amplitude R and phase θ processing paths. Therefore, there is a need for techniques to determine and correct for delays in the amplitude R and phase θ processing paths. There is a need to estimate and correct for these timing misalignments in an accurate manner.